Inverse miniemulsion periphery RAFT polymerization: a facile pathway to polymeric nanocapsules

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Embargoed until 2015-06-30
Copyright: Utama, Robert
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Abstract
A novel synthetic pathway called inverse miniemulsion periphery RAFT polymerization (IMEPP) is reported herein. In comparison to other available methods to synthesize polymeric nanocapsules, IMEPP offers advantages such as: 1) eliminating the need for non-biocompatible surfactants, 2) eliminating the possibility to produce solid nanoparticles, 3) a reaction free core-environment, suitable for the encapsulation of fragile molecules, 4) excellent control over the size and the shell thickness of the nanocapsules and 5) versatility towards different monomers and various post-polymerization reactions. IMEPP produces hollow or loaded polymeric nanocapsules in a one-pot approach. The diameter of the soft, spherical template generated in the inverse miniemulsion can be controlled efficiently by varying the quantity of the individual components. IMEPP utilizes amphiphilic block copolymers which serve as both stabilizers and macroRAFT agents. The subsequent production of the polymeric shell is controlled via RAFT polymerization, initiated and growing away from the outer surface of the droplet. The properties (such as thickness, porosity and shell functionalities) were confirmed to be controllable by varying the RAFT polymerization conditions. It was also reported, for the first time, how SAXS can be employed to study the evolution of shell thickness over time and the morphologies of the resulting polymeric nanocapsules. The resulting nanocapsules were particularly aimed for drug delivery applications. Two different molecules, BSA and gemcitabine, were successfully encapsulated with high encapsulation and loading efficiency. At the same time, two different release mechanisms were designed. For BSA-loaded nanocapsules, the release was diffusion controlled with the unwanted, initial burst release (commonly occurring in loaded-vesicles) completely eliminated. In contrast, gemcitabine-loaded nanocapsules underwent burst release mechanism in the presence of reducing agents (such as glutathione in biological cells). Post-polymerization modifications of the shell were also conducted and reported. Acid-catalyzed hydrolysis was successfully conducted to produce pH responsive (anionic) nanocapsules. Similarly, aminolysis was also used to produce pH responsive (cationic) nanocapsules. The gemcitabine-loaded nanocapsules were also modified to introduce sugar functionalities on the shell. Gemcitabine loaded within the resulting glycopolymer nanocapsules was found to be more cytotoxic in comparison to free gemcitabine when tested against pancreatic cancer cells (AsPC-1).
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Author(s)
Utama, Robert
Supervisor(s)
Stenzel, Martina
Zetterlund, Per
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Publication Year
2014
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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